Re: How can I get a PV from an external server from inside a docker container?

[Florian Feldbauer via Tech-talk <tech-talk at aps.anl.gov>]

Hey,

the issue is, that EPICS uses UDP broadcasts to find and connect to other PVs.

If the docker container is running on the same machine as your local host IOC, these two are connected via the virtual docker network therefore UDP broadcasts can be send between those two.
But broadcasts are not forwarded from the virtual docker network to your physical network, thus your container cannot establish a connection with the external host.

The only way I got this working so far, is to create the docker container with the `-net host` option.
Using the MACVLAN network driver might work too. I never had the time to look into it.

Best regards,
Florian

Am 25.03.2024 um 14:55 schrieb Carsten Winkler via Tech-talk:

Hello,

I have 3 SoftIOCs.
    1.) local host       = 193.100.100.100 with PV: "local_pv"
    2.) external host  = 192.200.200.200 with PV: "external_pv"
    3.) docker container    on local host   with PV: "docker_pv"

From local host I can read all PVs (caget local_pv external_pv docker_pv). 👍
From inside the docker container I can read the local_pv and the docker_pv
but not the external_pv. 🤔

Here is my docker compose configuration:

services:
    epicsbase:
       image: softioc
       container_name: epicsbase
       volumes:
          - ./epicsbase/db:/usr/local/db
       working_dir: /usr/local/epics
       command:
          - /bin/sh
          - -c
          - |
          echo start first Soft IOC
          screen -d -m /usr/local/epics/epics-base/bin/linux-x86_64/softIoc -D /usr/local/epics/epics-base/dbd/softIoc.dbd -d /usr/local/db/test.db
          tail -f /dev/null # keep alive
       networks:
          - ioc-net
networks:
    ioc-net:

From inside the docker container I have also already tried EPICS_CA_AUTO_ADDR_LIST / EPICS_CA_ADDR_LIST. Unfortunately without success.
With and without these environment variables I only get the local_pv and the docker_pv.

How can I also read the external_pv from inside the docker container?

Best regards
Carsten

-- 
Ruhr-Universität Bochum
AG der Experimentalphysik I
Dr. Florian Feldbauer
NB 2/131 / Fach 125
Universitätsstr. 150
D-44801 Bochum

Office: NB 2/134
Phone:  (+49)234 / 32-23563
Fax:    (+49)234 / 32-14170
https://paluma.ruhr-uni-bochum.de